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libr/egg/t/README.md

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Example .r programs for the r_egg compiler (ragg2)

These are short, self contained .r programs that showcase the syntax accepted by ragg2. They are intended as both documentation and as a quick sandbox for experimenting with the compiler.

Each file can be compiled with:

ragg2 -a <arch> -b <bits> -k <os> -s FILE.r

Useful backends for experimenting:

-a trace           pseudo-assembly that mirrors the IR the parser
                   emits (great for understanding the compiler)
-a esil            stack based intermediate language, readable
                   and directly consumable by the r2 ESIL VM
-a x86 -b 32/64    native x86 / x86-64 assembly
-a arm -b 32/64    native ARM / AArch64 assembly

Files

  • hi.r smallest possible "write then exit" program
  • hello.r loop that repeatedly writes "Hello World"
  • exit.r raw inline assembly mixed with the high-level language
  • write.r syscall declarations with string literals
  • arith.r arithmetic expressions and operator precedence
  • regs.r direct native-register access via the .regname syntax
  • alias.r register aliases defined with the @alias directive
  • cond.r conditional statements: if, if/else style, while
  • customsyscall.r overriding the @syscall body with inline asm

Language cheat sheet

/* comment */  //comment    #comment
: raw asm line                   ; any line starting with ":" is passed
                                  through verbatim to the assembler

name@global(S,F) { body }        ; function with S byte stackframe
                                  and F bytes reserved for constants
name@syscall(N);                 ; declare name as a syscall number
name@alias(value)                ; textual alias: .name -> value
name@fastcall(addr)              ; call a function at addr via fastcall
@syscall() { body }              ; override the generated syscall body

.var0, .var4, .varN              ; local variables at frame offset N
.arg0, .arg4                     ; function arguments
.ret                             ; return register (retvar)
.regN                            ; generic register by index
.%rax, .%ecx, .%x0, ...          ; raw native register (verbatim)
.foo (after foo@alias(...))      ; alias-resolved register/symbol
(any other .name raises an error)

var = expr                       ; assignment
var += expr, -=, *=, /=          ; compound assignment
var = *addr                      ; dereference (read)
fn(arg1, arg2, ...)              ; function / syscall call

Example compile and inspect

ragg2 -a esil  -s t/hi.r
ragg2 -a trace -s t/arith.r
ragg2 -a x86 -b 64 -s t/regs.r